Cannot increase Samples past 1
Remove Drivers

You may have somehow added a driver to that value (e.g typing #frame in the field).


  Drivers can use properties, numbers, transformations, and scripts, to control the values of properties.


By assinging a driver to the Samples quantity, you are basically telling Blender to pick the value from somwhere else (e.g. scripted expressions,...).The manual inputs will be overrided till the driver is present.



To delete a driver, right click on the field and choose the option from the pop-up menù.